Effects of different types of palatal lateral excisions on growth and development of maxilla and dental arch

Abstract

Objective: This study aimed to explore the effects of different types of palatal lateral excisions on the growth and development of the maxilla and dental arch, and to investigate the underlying mechanisms.

Methods: A total of 112 3-week-old Sprague-Dawley (SD) male rats were randomly divided into a control and 3 experimental groups: the mucoperiosteal denudation group, the mucosal flap excision group, and the periosteum excision group. In the experimental groups, bilateral mucoperiosteal, mucosal flap and periosteum were excised respectively in the lateral one half of the palate. Four rats in each group were randomly chosen for sacrifice every two weeks. The maxilla was dissected following the excision. The widths of the maxilla and dental arch were measured and the histological phenomena were investigated at different phases. At the same time, 12 animals in each group were sequentially injected with calcein every two weeks. Three animals in each group, whose fluorescent labeling was used, were sacrificed for investigating bone formation at Week 8 following injection.

Results: (1) Each experimental group presented the constriction of the maxilla and dental arch. The upper first molars in the experimental groups inclined medially. The mucoperiosteal denudation group showed the largest degree of effect followed by the periosteum excision group. The indices of the mucosal flap excision group, which retained the structures of the periosteum layer, had the most approximate values to the control group; (2) Different histological changes among the experimental groups were detected. The fibers penetrated into the palatal bone as Sharpey's fibers in the mucoperiosteal denudation group. The pattern of bone deposition was the bundle type. Sharpey's fibers were not found in the mucosal flap and periosteum excision groups and the depositions of palatal bone were the lamellar type as those in the control group; (3) The rates of bone deposition in the experimental groups decreased compared with the control group. The rates in different phases were the most approximate values to those of the control group in the mucosal flap excision group, which has the same structure of periosteum as the control group.

Conclusion: There were different effects on the growth and development of the maxilla and dental arch in different types of palatal lateral excisions. Periosteum is important for bone formation and deposition pattern. The prevention of Sharpey's fibers forming and attaching to the palatine can effectively avert the following malformation.

Fig. 1

Diagram of the rat palate. Hatched areas are the soft tissue excision areas. Operative incision began at posterior margin of anterior palatine foramen and ended on the level of distal surface of the maxillary second molar. Bilateral halves of palatal mucoperiosteum, mucosal flap and periosteum were excised in three experimental groups

Fig. 2

Diagram of the measuring points. The middle points of enamelcement junction between buccal and lingual surfaces of the maxillary first molar assumed as the rotation center of teeth were defined as A and A′ points. The distance between A and A′ points represented the width of maxilla (AA′). On the vertical lines to the above connecting lines, there are 30 mm points higher defined as B and B′ points, and the distance between B and B′ points represented the width of dental arch (BB′). BB′ value minus AA′ value was defined as CC′, representing the degree of tooth obliquity. The smaller CC′ value was, the more serious the first molar introversion was

Fig. 3

Chronological changes of maxilla width (AA′) (a), dental arch width (BB′) (b), and the degree of the upper first molar introversion (CC′) (c) in the four groups that were measured on different phases Group I: Mucoperiosteal denudation group; Group II: Mucosal flap excision group; Group III: Periosteum excision group

Fig. 3

Chronological changes of maxilla width (AA′) (a), dental arch width (BB′) (b), and the degree of the upper first molar introversion (CC′) (c) in the four groups that were measured on different phases Group I: Mucoperiosteal denudation group; Group II: Mucosal flap excision group; Group III: Periosteum excision group

Fig. 3

Chronological changes of maxilla width (AA′) (a), dental arch width (BB′) (b), and the degree of the upper first molar introversion (CC′) (c) in the four groups that were measured on different phases Group I: Mucoperiosteal denudation group; Group II: Mucosal flap excision group; Group III: Periosteum excision group

Fig. 4

Frontal section of the rat palate (H & E staining) (a) Control group (Week 8). The periodontal fibers were fanned out into the gingiva and the deeper layers of the palatal connective tissues. Sharpey’s fibers were not found. The palatal bone was of the lamellar type; (b) Mucoperiosteal denudation group (Week 8). Sharpey’s fibers created a firm attachment of the scar tissues to the bone. The palatal bone was of the bundle type; (c) Mucosal flap excision group (Week 8). The periodontal ligament showed less attachment to the mucoperiosteal connective tissue. The palatal bone was of lamellar type; (d) Periosteum excision group (Week 4). A thin layer of regenerated periosteum appeared in the operation area; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The surface of the palatine was flat. PF: Periodonal fibers; LB: Lamellar type bone; SF: Sharpey’s fibers; BB: Bundle type bone; P: Periosteum

Fig. 4

Frontal section of the rat palate (H & E staining) (a) Control group (Week 8). The periodontal fibers were fanned out into the gingiva and the deeper layers of the palatal connective tissues. Sharpey’s fibers were not found. The palatal bone was of the lamellar type; (b) Mucoperiosteal denudation group (Week 8). Sharpey’s fibers created a firm attachment of the scar tissues to the bone. The palatal bone was of the bundle type; (c) Mucosal flap excision group (Week 8). The periodontal ligament showed less attachment to the mucoperiosteal connective tissue. The palatal bone was of lamellar type; (d) Periosteum excision group (Week 4). A thin layer of regenerated periosteum appeared in the operation area; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The surface of the palatine was flat. PF: Periodonal fibers; LB: Lamellar type bone; SF: Sharpey’s fibers; BB: Bundle type bone; P: Periosteum

Fig. 4

Frontal section of the rat palate (H & E staining) (a) Control group (Week 8). The periodontal fibers were fanned out into the gingiva and the deeper layers of the palatal connective tissues. Sharpey’s fibers were not found. The palatal bone was of the lamellar type; (b) Mucoperiosteal denudation group (Week 8). Sharpey’s fibers created a firm attachment of the scar tissues to the bone. The palatal bone was of the bundle type; (c) Mucosal flap excision group (Week 8). The periodontal ligament showed less attachment to the mucoperiosteal connective tissue. The palatal bone was of lamellar type; (d) Periosteum excision group (Week 4). A thin layer of regenerated periosteum appeared in the operation area; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The surface of the palatine was flat. PF: Periodonal fibers; LB: Lamellar type bone; SF: Sharpey’s fibers; BB: Bundle type bone; P: Periosteum

Fig. 4

Frontal section of the rat palate (H & E staining) (a) Control group (Week 8). The periodontal fibers were fanned out into the gingiva and the deeper layers of the palatal connective tissues. Sharpey’s fibers were not found. The palatal bone was of the lamellar type; (b) Mucoperiosteal denudation group (Week 8). Sharpey’s fibers created a firm attachment of the scar tissues to the bone. The palatal bone was of the bundle type; (c) Mucosal flap excision group (Week 8). The periodontal ligament showed less attachment to the mucoperiosteal connective tissue. The palatal bone was of lamellar type; (d) Periosteum excision group (Week 4). A thin layer of regenerated periosteum appeared in the operation area; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The surface of the palatine was flat. PF: Periodonal fibers; LB: Lamellar type bone; SF: Sharpey’s fibers; BB: Bundle type bone; P: Periosteum

Fig. 4

Frontal section of the rat palate (H & E staining) (a) Control group (Week 8). The periodontal fibers were fanned out into the gingiva and the deeper layers of the palatal connective tissues. Sharpey’s fibers were not found. The palatal bone was of the lamellar type; (b) Mucoperiosteal denudation group (Week 8). Sharpey’s fibers created a firm attachment of the scar tissues to the bone. The palatal bone was of the bundle type; (c) Mucosal flap excision group (Week 8). The periodontal ligament showed less attachment to the mucoperiosteal connective tissue. The palatal bone was of lamellar type; (d) Periosteum excision group (Week 4). A thin layer of regenerated periosteum appeared in the operation area; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The surface of the palatine was flat. PF: Periodonal fibers; LB: Lamellar type bone; SF: Sharpey’s fibers; BB: Bundle type bone; P: Periosteum

Fig. 5

Frontal section of the rat palate (trichrome staining) (a) Mucoperiosteal denudation group (Week 8). The periodontal fibers were fanned out into the scar tissues and connected with the collagenous fibers; (b) Mucosal flap excision group (Week 8). The periodontal fibers were not connected with the scar tissues; (c) Mucosal flap excision group (Week 8). The palatal bone was of lamellar type. Sharpey’s fibers were not found; (d) Periosteum excision group (Week 0). Periosteum was excised completely; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The palatal bone was of lamellar type. PF: Periodonal fibers; LB: Lamellar type bone

Fig. 5

Frontal section of the rat palate (trichrome staining) (a) Mucoperiosteal denudation group (Week 8). The periodontal fibers were fanned out into the scar tissues and connected with the collagenous fibers; (b) Mucosal flap excision group (Week 8). The periodontal fibers were not connected with the scar tissues; (c) Mucosal flap excision group (Week 8). The palatal bone was of lamellar type. Sharpey’s fibers were not found; (d) Periosteum excision group (Week 0). Periosteum was excised completely; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The palatal bone was of lamellar type. PF: Periodonal fibers; LB: Lamellar type bone

Fig. 5

Frontal section of the rat palate (trichrome staining) (a) Mucoperiosteal denudation group (Week 8). The periodontal fibers were fanned out into the scar tissues and connected with the collagenous fibers; (b) Mucosal flap excision group (Week 8). The periodontal fibers were not connected with the scar tissues; (c) Mucosal flap excision group (Week 8). The palatal bone was of lamellar type. Sharpey’s fibers were not found; (d) Periosteum excision group (Week 0). Periosteum was excised completely; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The palatal bone was of lamellar type. PF: Periodonal fibers; LB: Lamellar type bone

Fig. 5

Frontal section of the rat palate (trichrome staining) (a) Mucoperiosteal denudation group (Week 8). The periodontal fibers were fanned out into the scar tissues and connected with the collagenous fibers; (b) Mucosal flap excision group (Week 8). The periodontal fibers were not connected with the scar tissues; (c) Mucosal flap excision group (Week 8). The palatal bone was of lamellar type. Sharpey’s fibers were not found; (d) Periosteum excision group (Week 0). Periosteum was excised completely; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The palatal bone was of lamellar type. PF: Periodonal fibers; LB: Lamellar type bone

Fig. 5

Frontal section of the rat palate (trichrome staining) (a) Mucoperiosteal denudation group (Week 8). The periodontal fibers were fanned out into the scar tissues and connected with the collagenous fibers; (b) Mucosal flap excision group (Week 8). The periodontal fibers were not connected with the scar tissues; (c) Mucosal flap excision group (Week 8). The palatal bone was of lamellar type. Sharpey’s fibers were not found; (d) Periosteum excision group (Week 0). Periosteum was excised completely; (e) Periosteum excision group (Week 8). Scar tissues were connected with the periodontal fibers. The palatal bone was of lamellar type. PF: Periodonal fibers; LB: Lamellar type bone

Fig. 6

Frontal section of the rat palate (fluorescence microscope image; calcein) (a) Control group. Fluorescence labeling lines were arranged from the side of the nose to the side of the palatine regularly; (b) Control group. Irregular fluorescence labeling band was found on the median suture of palatine, corresponding to the last time of mark; (c) Mucoperiosteal denudation group. Massive irregular fluorescent labeling markers could be observed adjoining the side of the nose. Flexed marker line aligned on the side of the palatine; (d) Mucosal flap excision group. The regular fluorescence labeling lines corresponding to the injection time (Weeks 0, 2 , 4 , 6 , 8) were observed from the side of the nose to the side of the palatine. The labeling lines showed wrinklier; (e) Periosteum excision group. Arrow shows the fluorescence labeling lines of the 0~2 weeks, which were dispersed and irregular. The fluorescence labeling lines of 4~8 weeks were relatively regularly distributed from the side of the nose to the side of the palatine

Fig. 6

Frontal section of the rat palate (fluorescence microscope image; calcein) (a) Control group. Fluorescence labeling lines were arranged from the side of the nose to the side of the palatine regularly; (b) Control group. Irregular fluorescence labeling band was found on the median suture of palatine, corresponding to the last time of mark; (c) Mucoperiosteal denudation group. Massive irregular fluorescent labeling markers could be observed adjoining the side of the nose. Flexed marker line aligned on the side of the palatine; (d) Mucosal flap excision group. The regular fluorescence labeling lines corresponding to the injection time (Weeks 0, 2 , 4 , 6 , 8) were observed from the side of the nose to the side of the palatine. The labeling lines showed wrinklier; (e) Periosteum excision group. Arrow shows the fluorescence labeling lines of the 0~2 weeks, which were dispersed and irregular. The fluorescence labeling lines of 4~8 weeks were relatively regularly distributed from the side of the nose to the side of the palatine

Fig. 6

Frontal section of the rat palate (fluorescence microscope image; calcein) (a) Control group. Fluorescence labeling lines were arranged from the side of the nose to the side of the palatine regularly; (b) Control group. Irregular fluorescence labeling band was found on the median suture of palatine, corresponding to the last time of mark; (c) Mucoperiosteal denudation group. Massive irregular fluorescent labeling markers could be observed adjoining the side of the nose. Flexed marker line aligned on the side of the palatine; (d) Mucosal flap excision group. The regular fluorescence labeling lines corresponding to the injection time (Weeks 0, 2 , 4 , 6 , 8) were observed from the side of the nose to the side of the palatine. The labeling lines showed wrinklier; (e) Periosteum excision group. Arrow shows the fluorescence labeling lines of the 0~2 weeks, which were dispersed and irregular. The fluorescence labeling lines of 4~8 weeks were relatively regularly distributed from the side of the nose to the side of the palatine

Fig. 6

Frontal section of the rat palate (fluorescence microscope image; calcein) (a) Control group. Fluorescence labeling lines were arranged from the side of the nose to the side of the palatine regularly; (b) Control group. Irregular fluorescence labeling band was found on the median suture of palatine, corresponding to the last time of mark; (c) Mucoperiosteal denudation group. Massive irregular fluorescent labeling markers could be observed adjoining the side of the nose. Flexed marker line aligned on the side of the palatine; (d) Mucosal flap excision group. The regular fluorescence labeling lines corresponding to the injection time (Weeks 0, 2 , 4 , 6 , 8) were observed from the side of the nose to the side of the palatine. The labeling lines showed wrinklier; (e) Periosteum excision group. Arrow shows the fluorescence labeling lines of the 0~2 weeks, which were dispersed and irregular. The fluorescence labeling lines of 4~8 weeks were relatively regularly distributed from the side of the nose to the side of the palatine

Fig. 6

Frontal section of the rat palate (fluorescence microscope image; calcein) (a) Control group. Fluorescence labeling lines were arranged from the side of the nose to the side of the palatine regularly; (b) Control group. Irregular fluorescence labeling band was found on the median suture of palatine, corresponding to the last time of mark; (c) Mucoperiosteal denudation group. Massive irregular fluorescent labeling markers could be observed adjoining the side of the nose. Flexed marker line aligned on the side of the palatine; (d) Mucosal flap excision group. The regular fluorescence labeling lines corresponding to the injection time (Weeks 0, 2 , 4 , 6 , 8) were observed from the side of the nose to the side of the palatine. The labeling lines showed wrinklier; (e) Periosteum excision group. Arrow shows the fluorescence labeling lines of the 0~2 weeks, which were dispersed and irregular. The fluorescence labeling lines of 4~8 weeks were relatively regularly distributed from the side of the nose to the side of the palatine